Magnetic components used in electronic devices such as electromagnetic relays (also referred to as relays) are plated with nickel to provide corrosion resistance. FIG. 30 is a perspective view of a relay 200 known in the art. The relay 200 includes a yoke 201, an iron piece 202, and an iron core 203, which are magnetic components plated with nickel. Nickel (Ni) plating covers the surfaces of the components. The Ni plating layers need to be thicker to improve corrosion resistance. However, thicker Ni plating layers can affect mating of the components.
Thin Ni plating layers can also cause problems. When, for example, an electric contact in a sealed relay is open and closed under high voltage and high current, it generates arc heat, which then produces nitric acid. Such nitric acid can corrode the plating, and can form patina on the surface of the magnetic component. As this reaction proceeds, the relay can malfunction.
Further, a relay including a sliding part (hinge) can have its operating characteristics varying greatly when the hinge part is mechanically worn by sliding. To overcome this, a lubricating oil is applied to the hinge part during assembly of the relay. However, no lubricating oil is added again to the hinge part during the service life of the relay. The hinge part can thus wear with time.
In response to such difficulties associated with the thickness of Ni plating and its corrosion resistance, techniques using chrome have been developed. Patent Literature 1 describes a soft magnetic stainless steel containing chrome used for an iron core of a relay. Patent Literature 2 describes an electromagnetic material containing chrome used for a relay. The stainless steel described in Patent Literature 1 and the electromagnetic material described in Patent Literature 2 contain chrome, and eliminate difficulties associated with the thickness.
Techniques using chrome have also been developed to achieve wear resistance. Patent Literatures 3 to 5 describe chromized chains and chromized pins for chains. The techniques described in Patent Literatures 3 to 5 use diffusion-coating of chrome on the surface of a chain or a chain pin to improve wear resistance. The chromizing allows chrome to diffuse and penetrate into the base material, and thus prevents the thickness from increasing.
Patent Literature 6 describes a method of chromizing. With the technique described in Patent Literature 6, a mixture of chrome metal powder and at least one metal powder of an element selected from the group consisting of Zn, W, Ti, and Mo is used to form a chrome diffusion layer. The technique described in Patent Literature 6 can form a very thick chrome diffusion layer, thus providing improved corrosion resistance.